1. Field of the Invention
The present invention relates generally to linear compressors, and more particularly to an apparatus and method for controlling a linear compressor, which prevents the collision of a piston with a valve to improve operational efficiency of the linear compressor during operation of the linear compressor.
2. Description of the Prior Art
FIG. 1 is block diagram of a conventional linear compressor control apparatus.
Referring to FIG. 1, the conventional linear compressor control apparatus comprises a core 10, first and second coils 12 and 13, and a signal processing unit 20. The core 10 of a magnetic substance operates in conjunction with a machine for detecting a position of a piston. The first and second coils 12 and 13 are symmetrically wound around the outside of the core 10. The signal processing unit 20 detects and outputs the change of the core position according to voltages induced in the first and second coils 12 and 13.
The signal processing unit 20 comprises a first full-wave rectifying unit 21, a second full-wave rectifying unit 22, a differential amplifying unit 23, a filter unit 24 and a peak detection unit 25. The first full-wave rectifying unit 21 full-wave rectifies the voltage induced in the first coil 12, and the second full-wave rectifying unit 22 full-wave rectifies the voltage induced in the second coil 13. The differential amplifying unit 23 amplifies the voltage difference between the rectified voltages of the first and second full-wave rectifying units 21 and 22. The filter unit 24 removes high frequency component of an output signal from the differential amplifying unit 23. The peak detection unit 25 detects the maximum value and the minimum value of an output signal from the filter unit 24, and transmits the detected values to a control unit.
The operation of the conventional apparatus having the above construction is described.
When an AC power voltage of several KHz is applied to both the first and second coils 12 and 13 from the outside, if the position of the core 10 is changed due to the change of position of the machine for detecting the position of the piston, voltages proportional to the change in position of the core 10 are induced in the first and second coils 12 and 13. The voltages induced in the first and second coils 12 and 13 are full-wave rectified by the first and second full-wave rectifying units 21 and 22, respectively, and the rectified results are applied to input terminals of the differential amplifying unit 23.
The differential amplifying unit 23 amplifies the voltage difference between the full-wave rectified voltages of the first and second full-wave rectifying units 21 and 22, and outputs the amplified results to the filter unit 24. Then, the filter unit 24 removes the high frequency component of the output signal from the differential amplifying unit 23, amplifies the resulting signal, and outputs the amplified signal to the peak detection unit 25. The peak detection unit 25 full-wave rectifies the output signal from the filter unit 24 and outputs the rectified signal to the microcontroller 30. The microcontroller 30 controls the stroke of the linear compressor in response to the output signal from the peak detection unit 30, which is obtained by full-wave rectifying the output signal from the filter unit 24.
The conventional linear compressor control apparatus has a constant stroke by controlling only the stroke of the piston of the linear compressor according to the above construction. However, the conventional linear compressor control apparatus is disadvantageous in that it cannot maintain a constant top clearance with respect to the position of its top dead center due to a characteristic of the linear compressor that the center position of the piston is changed according to a load.